The present invention relates generally to the field of thyratrons, and more particularly to thyratrons providing low inductance, high current, long lifetime switches.
Conventional thyratrons supplied commercially for high power switch applications are fabricated in a cylindrical geometry, using sealed-off ceramic/metal tubes. There have been several major obstacles in previous attempts to produce low inductance, high current thyratrons based on commercial thyratron technology. One limitation is associated with the cylindrically symmetrical tube geometry that has been used, which is inherently higher inductance than a linear (stripline) geometry. A closely related limitation is the use of permanent ceramic-to-metal seals in thyratron construction, which successfully permits high temperature bakeout of the tube to yield a long-life, sealed-off structure. However, this type of construction is subject to thermally induced stress, which restricts the maximum scale dimensions of the tube and also prevents the use of an elongated (linear) geometry. Finally, studies of large experimental thyratrons built for low inductance and very high rate of rise of current have shown that the plasma often does not form uniformly within the tube. Instead, small, high current density regions are formed, which produce cathode damage and also result in an inductance that is higher than the value calculated on the basis of a uniform plasma.
U.S. patents showing the state of the art include U.S. Pat. No. 2,813,999 to Foin, Jr., which discloses a high power RF switch tube of rectangular cross section. It comprises a predetermined length of hollow metallic wave guide which includes an anode, cathode, and control grid. U.S. Pat. No. 3,845,427 to Schubert is directed to a thyratron switch in a waveguide. The device of this patent includes a cone such that the overall combination acts as a gas tetrode. A thyratron tetrode is also dislcosed in U.S. Pat. No. 2,953,716. (U.S. Pat. No. 3,084,282) is directed to a thyraton having fast switching characteristics and Krefft (U.S. Pat. No. 3,349,283) relates to a hydrogen filled thyratron capable of operating at very high voltages.